Messaging systems, such as instant messaging systems and short message service (“SMS”) systems, allow users to communicate with each other by exchanging messages. When a user first joins a messaging service, or returns to a messaging service after a period of inactivity, the user may not be aware of which other users are reachable through the messaging service. If the user does not engage with other users in the period after they join the messaging service, there may be an increased likelihood that the user will become inactive.